Page 450 - Small Animal Internal Medicine, 6th Edition

422 PART III Digestive System Disorders

tissue infiltrates are found, they can sometimes be aspirated defects (e.g., growths and radiolucent foreign objects),
by the fine-needle technique. pyloric lesions preventing gastric emptying, and infiltrative
VetBooks.ir INDICATIONS FOR CONTRAST- lesions may be seen using this method. However, normal
peristalsis, ingesta, or gas bubbles may resemble an abnor-
ENHANCED GASTROGRAMS
films before the clinician can diagnose disease.
Since the advent of ultrasonography, contrast gastrograms are mality, so a change must be seen on at least two separate
seldom required. However, they may be considered in vomit- Contrast-enhanced gastrograms are very insensitive for
ing animals when ultrasound studies and plain abdominal detecting ulcers and useless for erosions. Ulcers are docu-
radiographs are unrevealing. It is primarily useful to detect mented radiographically if barium is seen to enter the gastric
gastric masses/foreign bodies and gastric motility problems. or duodenal wall or if a persistent spot of barium is identi-
Endoscopy is usually a better choice to examine the stomach fied in the stomach long after the organ has emptied itself
unless there is a primary motility problem (rare). of the contrast agent. The duodenum should be scrutinized
in a search for constrictions and infiltrative lesions because
Technique many vomiting animals have disease there (e.g., inflamma-
The animal should not be allowed to eat for at least 12 tory bowel disease, tumors) rather than in the stomach (see
hours (preferably 24 hours) before the procedure, and feces Chapter 31).
should be removed with enemas. Plain radiographs should
be obtained immediately before the contrast-enhanced films INDICATIONS FOR CONTRAST-
to verify that the abdomen has been properly prepared, that ENHANCED STUDIES OF
the radiographic technique is correct, and that the diagno- THE SMALL INTESTINE
sis cannot be made on the basis of the plain radiographic Vomiting is the principal albeit rare reason for performing
findings alone. Liquid barium sulfate is then administered contrast studies of the upper small intestine. Contrast-
orally (8-10 mL/kg in small dogs and cats and 5-8 mL/ enhanced radiographs can typically distinguish anatomic
kg in large dogs). Iohexol can be administered orally (i.e., from physiologic ileus but are almost never needed for that
700-875 mg I/kg, which is usually about 1 4 to 1 2 mL/kg). purpose. Orad obstructions are easier to demonstrate than
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The agent should be administered via a stomach tube to aborad ones. If a very aborad obstruction is suspected (e.g.,
ensure adequate gastric filling and optimal evaluation of the ileocolic intussusception), a barium enema (or preferably
stomach. The animal should not receive motility-altering ultrasonography) is often better than an upper GI contrast
drugs (e.g., xylazine, ketamine, parasympatholytics) that series. Although linear foreign objects usually produce subtle
delay outflow. findings on plain radiographs, they often cause a classic
Immediately after barium administration, radiographs “pleating” or “bunching” of the intestines on contrast films
are taken in left and right lateral plus DV and VD projec- (see Fig. 31.12, C).
tions. Lateral and DV projections should be obtained again Animals with diarrhea seldom benefit from contrast
at 15 and 30 minutes and perhaps hourly from 1 to 3 hours. studies of the intestines because normal radiographic find-
The right lateral view causes barium to pool in the pylorus, ings do not exclude severe intestinal disease. Even if radio-
the left lateral view causes it to pool in the gastric body, the graphic findings indicate infiltrative disease, it is still
DV view causes it to pool along the greater curvature, and necessary to obtain a biopsy specimen to determine the
the VD view allows better evaluation of the pylorus and cause. It is usually more cost-effective to skip contrast-
antrum. Double-contrast gastrograms provide more detail enhanced radiographs and perform endoscopy or surgery.
than single-contrast gastrograms. They are performed by Use of iodinated contrast agents (preferably iohexol) is
administering and immediately removing barium via a reasonable if an alimentary tract perforation is suspected.
stomach tube and then insufflating the stomach with gas However, if spontaneous septic peritonitis is strongly sus-
until it is mildly distended. pected, it can usually be definitively diagnosed by ultrasound-
If available, fluoroscopy is best performed immediately guided abdominocentesis and fluid analysis, which reveals
after administration of the barium. It can be used to evaluate septic peritonitis. If ultrasound is unavailable and blind
gastric motility, gastric outflow, and the maximal opening abdominocentesis is unrevealing in such a patient, it is often
size of the pylorus. If the animal is fed barium mixed with better to perform a thorough exploratory laparotomy than
food (recommended only if gastric outflow tract obstruction contrast-enhanced radiography.
is suspected despite normal liquid barium study findings), Contrast CT of the GI tract is possible but is seldom
gastric emptying will be markedly delayed compared with needed and can be difficult to critically evaluate.
that seen when the animal is fed liquid barium.
Technique
Findings Liquid barium sulfate is administered as described for
Gastric emptying is considered delayed if liquid barium does contrast-enhanced gastrography. Lateral and VD radio-
not enter the duodenum within 15 to 30 minutes after graphs should be obtained immediately and then 30, 60, and
administration or if the stomach fails to almost completely 120 minutes after barium administration. Additional films
empty the liquid barium within 3 hours. Luminal filling are obtained as necessary. The study is completed once